Rigid-Plastic Approximation to Predict Plastic Motion Under Strong Earthquakes

The paper shows that the rigid{plastic oscillator can be used to evaluate the maximum plastic displacement of any elastic{plastic oscillator under any earthquake. Motivated by this result a rigid{plastic response spectrum is introduced, which provides an easy method to calculate the maximum plastic displacement of a rigid{plastic oscillator for any given earthquake. Such a spectrum is easier to construct than the elastic{plastic response spectrum or the classical elastic one. By means of appropriate formulas presented in the paper, the rigid{plastic response spectrum can be used to determine a realistic upper bound to the maximum plastic displacement of any elastic{plastic oscillator under the given earthquake.